1. Field of the Invention
The present invention relates to a method of manufacturing a high-speed bipolar transistor, high-speed bipolar LSI or the like and, more particularly, to a method of manufacturing a bipolar transistor with self-aligned external base and emitter regions.
2. Description of the Related Art
An SST-1A process developed by NTT (Nihon Telephone and Telegram Inc.) is known as a conventional method of manufacturing a bipolar transistor wherein an external base region and an emitter region are self-aligned. This process is described in IEDM-INTERNATIONAL ELECTRON DEVICES MEETING 1983, pp. 16, T. Sakai and M. Suzuki. According to the SST-1A process, the emitter region and the external base region can be formed in self-alignment. According to this method, however, four polysilicon deposition steps are required. In addition, a large number of difficult steps such as etch-back are required. For these reasons, it is difficult to stably manufacture uniform bipolar transistors. Therefore, manufacturing cost of the bipolar transistor is undesirably increased.
In the method of manufacturing the bipolar transistor described above, the emitter region and the external base region cannot be easily self-aligned with high precision and good controllability.